This invention relates to a process for producing a coal-water slurry of high concentration of coal by reducing the particle size of the coal (hereinafter referred to generally as "pulverizing" and sometimes as "crushing" or "grinding") in a specific manner.
The process of mixing pulverized coal with water and rendering the mixture into a high-concentration slurry which is of low viscosity whereby transfer thereof by pumping is possible, and which, moreover, has a fluidity such that the coal particles will not settle and separate out, in general, is difficult. For this reason, measures such as the addition of additives for facilitating this process have heretofore been resorted to. At the same concentration of a coal-water slurry, a tendency of the slurry viscosity to increase with decrease in the coal particle size is exhibited. For this reason, the preparation of a high-concentration slurry for the purpose of direct combustion is difficult.
As a cumulative result of our research directed toward the objective of producing high-concentration slurries, we have discovered that, by carrying out a specific pulverizing process to finely pulverize coal and thereby to obtain a specific particle-size constitution or distribution, it is possible to further increase the coal concentration of coal-water slurries having fluidity which have heretofore been obtained.